#include <stdio.h>
#include <stdbool.h>

long get_long(void);
bool bad_limits(long begin, long end, long low, long high);
double sum_squares(long a, long b);

int main(void)
{
	const long MIN = -10000000L;
	const long MAX = +10000000L;
	long start;
	long stop;
	double answer;
	
	printf("This is program computes the sum of the squares of "
			"integers in a range.\nThe lower bound should not "
			"be less than -10000000 and\nthe upper bound "
			"should not be more than +10000000.\nEnter the "
			"limits (enter 0 for both limits to quit):\n"
			"lower limit: ");
	start = get_long();
	printf("upper limit: ");
	stop = get_long();
	while (start != 0 || stop != 0)
	{
		if (bad_limits(start, stop, MIN, MAX))
			printf("Please try again.\n");
		else
		{
			answer = sum_squares(start, stop);
			printf("The sum of the squares of the integers ");
			printf("from %ld to %ld is %g\n", start, stop, answer);
		}
		printf("Enter the limits (enter 0 for both "
				"limits to quit):\n");
		printf("lower limit: ");
		start = get_long();
		printf("upper limit: ");
		stop = get_long();
	}
	printf("Done.\n");
	
	return 0;
}

long get_long(void)
{
	long input;
	char ch;
	
	while (scanf("%ld", &input) != 1)
	{
		while ((ch = getchar()) != '\n')
			putchar(ch);
		printf(" is not an integer.\nPlease enter an ");
		printf("integer value, such as 25, -178, or 3: ");
	}
	return input;
}

double sum_squares(long a, long b)
{
	double total = 0;
	long i;
	
	for (i = a; i <= b; i++)
		total += (double)i * (double)i;
	return total;
}

bool bad_limits(long begin, long end, long low, long high)
{
	bool not_good = false;
	if (begin > end)
	{
		printf("%ld isn't smaller than %ld.\n", begin, end);
		not_good = true;
	}
	
	if (begin < low || end < low)
	{
		printf("Values must be %ld or greater.\n", low);
		not_good = true;
	}
	
	if (begin > high || end > high)
	{
		printf("Values must be %ld or less.\n", high);
		not_good = true;
	}
	return not_good;
}
